Polystyrene viscous dissipation

A free radical catalyst or initiator is dissolved in the monomer which is then heated and stirred in a suitable vessel. The polymerisation is exothermic and dissipation of heat through cooling may be required. As the reaction progresses, tlie system becomes viscous making stirring difficult. The method is economical and the product is of high purity. The technique is used for preparing polyvinyl chloride. (PVC), polystyrene (PS) and polymethymethacrylate (PMMA). 

Energy dissipated by viscous flow in a macroscopic polymer forming process originates from friction between microscopic repeat units that constitute the polymer chain. The friction coefficient per repeat unit, the monomeric friction coefficient ( ), is a function of the geometry of the repeat unit and its chemistry. Molecules such as polystyrene and poly(methyl methacrylate) that possess stiff. 

---